DISPOSABLE DENTAL CONTRA-ANGLE

Abstract: A plastic, disposable, easy-to-assemble dental contra-angle (101) includes a one-piece body (103), a one-piece drive gear and shaft (117, 115), a driven gear (127), and a cap (135). The body (103) includes a sleeve portion (104), a neck (105), and a head (106). The neck (105) is bent about 10 DEG to 30 DEG . The forward end of the shaft (115) has an axial cavity (118) to provide additional flexibility. The shaft (115) is rotatably supported only at its forward end, and its free end bears against a slot (102) in the sleeve portion (104) when the contra-angle is not in use to reduce its degree of bending and to allow it to remain relatively relaxed.

Description: DISPOSABLE DENTAL CONTRA-ANGLE Field of Invention This invention relates to dental or prophylaxis angles, and, in particular, to a disposable dental contra- angle . Background of the Invention Dental angles carry dental bits such as prophy cups and brushes and burs . The angle enables dentists to reach more easily the various surfaces of a patient's teeth and thus facilitates the cleaning of the teeth. These angles generally include a body having a head thereon which has a major axis angled relative to the major axis of the body. The angle is commonly 90°. A drive gear and a driven gear are carried in the body in a meshing relationship. The driven gear carries a desired dental bit, such as a cleaning cup or a brush, which is to be used during the cleaning procedure. The body is slipped over the nose of a handpiece such as a Doriot type handpiece having a collet which receives the shaft of the drive gear. The collet holds the shaft, hence the angle, against axial movement. It also connects the drive gear to a motor, to rotate the drive gear, and thus the dental bit. The use of disposable dental angles reduces the labor, cost, and risks of sterilization. A particularly effective such disposable dental angle is disclosed in Bailey, U.S. Patent No. 5,156,547, the contents of which are hereby incorporated by reference. Contra-angles are often used by dental personnel for getting to difficult spots. Contra-angles include a head which is angled at a greater angle than the usual 90° with respect to the axis of the handpiece. Typically the head is angled 10° to 30°, often 15° to 22°, from normal to the handpiece axis. In some designs, the body of the angle includes a 15°-22° angle formed in it:; in others, an angieo adapter is provided between the angle and the handpiece. To drive the dental bit secured to the head, contra-angles generally have two drive shafts. A first drive shaft extends for the bend to the Doriot to be grasped by the Doriot handpiece collet . It includes a gear at its forward end. A second drive shaft extends from the bend to the head. It includes a gear at its back end which meshes with the drive gear of the first shaft and a gear at its front end, which meshes with the gear at the end of the dental bit shaft to drive the dental bit. Contra-angles are therefore complex, expensive, and made of expensive materials. No satisfactory disposable contra-angle is presently known. Summary of the Invention One object of the invention is to provide a disposable, inexpensive, rugged dental contra-angle. In accordance with one aspect of the present invention, generally stated, a disposable dental contra- angle is provided comprising a body formed of polymeric plastics material, the body having a sleeve with an open rear end, a head, and a neck between the sleeve and the head, a first axial bore in the sleeve and neck, the first axial bore including a bend of from 10° to 30°, a second axial bore in the head, the first and second bores communicating with each other at an intersection and being at an angle with respect to each other; a one-piece drive gear formed of polymeric plastics material, the drive gear including a gear part and a shaft, the shaft extending rotatably from the open rear end of the sleeve through the first bore; and a driven gear rotatably mounted in the head bore and operatively connected to the gear part of the drive gear, the driven gear including means for retaining a dental bit, characterized in that the shaft of the drive gear includes a hollow portion which is more flexible than the remainder of the shaft. Preferably, the hollow portion of the drive gear shaft extends rearwardly from the gear part of uhe drive gear to a point beyond the bend in the neck. Also preferably, the drive gear is inserted shaft first through the head, and the angle further includes cap means for closing the head as disclosed in U.S. Patent No. 5,156,547. In accordance with another aspect of the invention a disposable dental contra-angle is provided comprising a body formed of polymeric plastics material, the body having a sleeve with an open rear end, a head, and a neck between the sleeve and the head, a continuous axial bore in the sleeve and neck, the continuous bore comprising a first portion at the rear end of the sleeve and a second portion at a front end of the neck, the axial bore including a bend of from 10° to 30° between said first portion and said second portion; and a drive gear formed of polymeric plastics material, the drive gear including a gear part and a shaft, the shaft extending rotatably from the open rear end of the sleeve through the continuous axial bore, characterized in that the flexible shaft is rotatably supported solely by a bearing in the second portion of the continuous bore, so that the flexible shaft forms a substantial angle with respect to the axis of the first portion of the continuous bore when the contra-angle is removed from a handpiece. The flexible shaft is therefore flexed when the contra-angle is attached to a handpiece and relatively relaxed when the contra-angle is removed from the handpiece. Preferably, the drive gear shaft is movable in the body between a resting position wherein the shaft is bent less than 10° and a flexed position wherein the shaft is bent more than 10°; the shaft remaining in the resting position until a time for use of the contra-angle. Also preferably, the sleeve includes a slot into which the shaft extends in the resting position. The bend is preferably from 15° to 22°. The sleeve part of the body is preferably formed as a thin, flexible wall, the flexible shaft resting against the wall when the contra-angle is removed from a handpiece. Brief description of tne Figures FIG. 1 is a cross-sectional view of a disposable contra-angle having a single drive shaft in accordance with the present invention; and FIG. 2 is a view of the contra-angle' s drive shaft. Description of the Preferred Embodiment Referring to FIGS. 1-2, reference numeral 101 generally indicates a dental angle of the present invention. Angle 101 includes a one-piece body 103, a drive gear 117, a driven gear 127, and a cap 135. All the pieces are preferably molded of plastic so that angle 1 will be inexpensive to produce and thus disposable. This eliminates the need to sterilize angles and their associated bits between uses and thus eliminates any problem of cross-contamination between patients. It has been found that when dissimilar plastics are used for the body, cap, and gears, the angle operates more smoothly. Thus, it is preferred that the body and cap be made from a hard plastic such as a polycarbonate resin available from General Electric Co. under the trademark LEXAN, and that the gears be made from a more flexible plastic, such as a self-lubricating acetal copolymer available from Celanese Corp. under the trademark CELCON. Body 103 includes a sleeve portion 104, a neck 105, and a head 106. The wall thickness of the sleeve 104 is about 0.04". A slot 102 at the rear, open, end of the sleeve 104 is about 0.250" long and about 0.1" wide. The slot 102 is about twice as long as necessary to accommodate a standard positioning pin or finger on a standard Doriot type handpiece (not shown) . The length of the slot 102 and the thinness of the plastic sleeve wall in which it is formed permit the sleeve to expand slightly when it is forced onto a Doriot handpiece. The forward end of the sleeve portion 104 tapers to the neck portion 105, which is a smaller diameter cylinder coaxial with the sleeve 104. Neck 105 defines an angle of about 15°, as at 110, between the head end of the neck and the rear end of the sleeve. Bore 107, within neck 105 has a matching angle. The head portion 106 is formed as a cylinder at right angles to the neck 105, with the axis of the head 106 intersecting the axis of the neck 105. Body 103 and head 106 have axial bores 107 and 109, respectively. Body bore 107 is formed with several diameters. In the sleeve portion 104, bore 107 is formed with the same diameter as the nose of a standard Doriot handpiece. It tapers in the transition between sleeve 104 and neck 105, to a smaller diameter portion in the neck 105, then steps to a yet smaller diameter portion 107d through the forward part of the neck 105. The portion 107d acts as a journal for the drive gear shaft, as described hereinafter. Forward of the small diameter portion 107d, the bore 107 steps to a larger diameter portion, extending through the head portion 106 and forming an aperture 111 in the forward end of the head 106. Head bore 109 is formed at a 90° angle with respect to body bore 107d. At the lower end of the head 106 head bore 109 forms a blind hole 113 centered with respect to the head bore 109. The internal construction of the head is preferably as described in U.S. Patent No. 5,156,547. Drive gear 117 is formed integrally with a drive gear shaft 115. Drive shaft 115 includes a shoulder 119 spaced from the back of gear 117, defining a channel 155. Shaft 115 is stepped as indicated at 122 to define a single bearing surface 123 behind shoulder 119. The bearing surface 123 forms a smoothly rotatable fit with the forward portion of the neck portion 107d of the body bore 107. The remainder of the shaft 115 is of constant outer diameter. To provide the shaft 115 with additional flexibility, the forward end of the shaft, from gear 117 to a point beyond the area of maximum flexion of the shaft is provided with an axial cavity 118. The constant diameter rearward portion of the shaft 115 has an outer diameter of 0.0935", and the cavity 118 has a diameter of 0.0620" and a depth of 0.875" . If shaft: 115 were solid, it could bend to pass through angled bore 107d, but it would be less able to rotate about its axis effectively. When the shaft 115 is bent, it constantly has a compressed surface and a stretched surface opposite the compressed surface. When the shaft 115 rotates, the compressed and stretched surfaces are constantly changing. Thus, the surface of the shaft must be able to accommodate the constant change in stress placed upon it by the bend. The axial cavity 118 provides the shaft 115 with this pliability. Drive gear 117, which is fixed to one end of a drive gear shaft 115, is received in body bore 107 through aperture 111. Shaft 115 extends beyond the end of body 103 when inserted therein to facilitate the capture of drive shaft 115 by chuck jaws in a handpiece, such as a collet in a Doriot handpiece, as shown in U.S. Patent No. 5,156,547. Driven gear 127 is preferably identical with gear 27 of U.S. Patent No. 5,156,547. When inserted in head bore 109, driven gear 127 meshes with drive gear 117 to be driven thereby. Driven gear 127 receives a dental bit, such as a prophy cup 133. The gears 117 and 127 preferably form a 90° cog gear system as in U.S. Patent No. 5,156,547. A snap cap 135 is received in head bore 9 to lock gears 117 and 127 and their associated shafts in place in body 103. The snap cap 135 may preferably be identical with the cap 35 of U.S. Patent No. 5,156,547 and operates in the same way described therein to lock the parts together and form a barrier to ingress of matter into the body 103. Contra-angle 101 is assembled in the same manner as angle 1 of U.S. Patent No. 5,156,547. The bearing 123 is lubricated. The drive gear 117 and its shaft 115 are inserted into body 103 shaft first. The driven gear is then inserted into head 106 and the assembly is closed with cap 35. When shaft 115 is inserted into body 103, it stays generally straight. As shown in FIG. 1, the rearward end of tήe shaft 115 naturally extends into the slot 102 in the skirt 104, thereby reducing further the amount of bend in the shaft 115 during shipment and storage of the angle 101 to about 7.5°. The shaft thus stays in a relatively relaxed position until it is ready for use, which can be a considerable time after assembly. When the angle 101 is to be used, the shaft 115 is inserted into the collet of the handpiece, as is shown in FIG. 6 of U.S. Patent No. 5,156,547. Not until then does the shaft conform fully to the angle of neck 105. Because the shaft remains in its relaxed state until use, the shaft will not take a set. If the shaft were to be in its bent, flexed state from the time of assembly, the bend would tend to become set in the shaft. This would prevent contra-angle 101 from rotating smoothly and would greatly shorten the life of the shaft 115. By remaining in its relaxed, generally straight, position, the shaft remains more pliable, enabling it to take a constantly changing bend along its surface during use of the angle 101. The embodiment of FIGS. 7 and 8 has been run at 3,000 rpm for six hours before the shaft broke. This is far in excess of the time of use of the contra-angle on a single patient. It will be seen that although the use of the shaft 115 in the preferred construction of contra-angle provides many advantages, a similar shaft with a hollow portion to provide flexibility could be used in modifications of other types of disposable prophylaxis angles to provide a disposable contra-angle. Numerous variations, within the scope of the appended claims, will be apparent to those skilled in the art in light of the foregoing description and accompanying drawings .

Claims: CLAIMS : 1. A plastic, disposable, dental contra-angle comprising: a body having a sleeve with an open rear end, a head, and a neck between the sleeve and the head, a first axial bore in the sleeve and neck, the first axial bore including a bend of from 10° to 30°, a second axial bore in the head, the first and second bores communicating with each other at an intersection and being at an angle with respect to each other; a one-piece drive gear including a gear and a flexible shaft, the shaft extending rotatably from the open rear end of the sleeve through the first bore; and a driven gear rotatably mounted in the head bore and operatively connected to the drive gear, the driven gear including means for retaining a dental bit . 2. The contra-angle of claim 1, wherein the drive gear shaft includes a hollow portion. 3. The contra-angle of claim 1 or 2 wherein the hollow portion extends rearwardly from the drive gear. 4. The contra-angle of any of claims 1-3 wherein the hollow portion extends to a point beyond the bend in the neck. 5. The contra-angle of any of claims 1-4 wherein the shaft is molded of plastic. 6. The contra-angle of any of claims 1-5 wherein the shaft is inserted shaft first through an opening in the head, the angle further including cap means for closing the opening. 7. The contra-angle of any of claims 1-6 wherein the drive gear shaft is movable in the body between a resting position wherein the shaft is bent less than 10° and a flexed position wherein the shaft is bent more than 10°; the shaft remaining in the resting position until a time for use of the contra-angle. 8. The contra-angle of any of claims 1-7 wherein the drive gear shaft is movable between a resting position and a flexed position, the sleeve including a slot into which the shaft extends in the resting position until a time for use of the contra-angle. 9. The contra-angle of any of claims 1-8 wherein the bend is from 15° to 22°. 10. A dental contra-angle for attachment to a dental handpiece, said contra-angle comprising: a body having a generally cylindrical sleeve with an open rear end and a head, a first axial bore in the sleeve and a second axial bore in the head, said first and second bores communicating with each other at an intersection, the second bore being at an angle of from 100° to 120° with respect to the axis of said sleeve at said open rear end; a drive gear including a gear and a flexible shaft, said shaft extending rotatably from the open rear end of said sleeve through said first bore; means for causing said flexible shaft to be substantially coaxial with said sleeve at said open rear end of said sleeve when said contra-angle is attached to a handpiece and for causing said flexible shaft to form a substantial angle with respect to the axis of said sleeve at said open rear end of said sleeve when said contra-angle is removed from a handpiece, said means including said open rear end of said sleeve's being of sufficiently large diameter that said flexible shaft is flexed when said contra-angle is attached to a handpiece and relatively relaxed when said contra-angle is removed from the handpiece; and a driven gear rotatably mounted in said head bore and operatively connected to said drive gear, said driven gear including means for retaining a dental bit . 11. The contra-angle of claim 10, wherein the drive gear shaft includes a hollow portion extending rearwardly from the drive gear. 12. The contra-angle of claim 10 or 11 wherein the shaft is molded of plastics material. 13. A dental contra-angle for attachment to a dental handpiece, said contra-angle comprising: a body having a generally cylindrical sleeve with an open rear end and a head, a first axial bore in the sleeve and a second axial bore in the head, said first and second bores communicating with each other at an intersection, the second bore being at an angle of from 100° to 120° with respect to the axis of said sleeve at said open rear end; a drive gear including a gear and a flexible shaft, said shaft extending rotatably from the open rear end of said sleeve through said first bore, said open rear end of said sleeve being of sufficiently large diameter that said flexible shaft is flexed when said contra-angle is attached to a handpiece and relatively relaxed when said contra-angle is removed from a handpiece, said sleeve including a slot into which said shaft extends in said relatively relaxed position; and a driven gear rotatably mounted in said head bore and operatively connected to said drive gear, said driven gear including means for retaining a dental bit. 14. A disposable dental contra-angle comprising a body formed of polymeric plastics material, the body having a sleeve with an open rear end, a head, and a neck between the sleeve and the head, a continuous axial bore in the sleeve and neck, the continuous bore comprising a first portion at the rear end of the sleeve and a second portion at a front end of the neck, the axial bore including a bend of from 10° to 30° between said first portion and said second portion; and a drive gear formed of polymeric plastics material, the drive gear including a gear part and a shaft, the shaft extending rotatably from the open rear end of the sleeve through the continuous axial bore, characterized in that the flexible shaft is rotatably supported solely by a bearing in the second portion of the continuous bore, so that the flexible shaft forms a substantial angle with respect to the axis of the first portion of the continuous bore when the contra-angle is removed from a handpiece, whereby the flexible shaft is flexed when the contra-angle is attached to a handpiece and relatively relaxed when the contra-angle is removed from the handpiece. 15. The contra-angle of claim 14 wherein the drive gear shaft is movable in the body between a resting position wherein the shaft is bent less than 10° and a flexed position wherein the shaft is bent more than 10°, the shaft remaining in the resting position until a time for use of the contra-angle. 16. The contra-angle of claim 14 or 15 wherein the sleeve includes a slot into which the shaft extends in the resting position. 17. The contra-angle of any of claims 14-16 wherein the bend is from 15° to 22°. 18. The contra-angle of any of claims 14-17 wherein the sleeve part of the body is formed as a thin, flexible wall, the flexible shaft resting against the wall when the contra-angle is removed from a handpiece.

Inventors: BAILEY RONALD L, BAILEY, RONALD, L.
Applicants: YOUNG DENTAL MANUFACTURING COM, YOUNG DENTAL MANUFACTURING COMPANY
Application year: 1994
Main classification: A61C3
IPC codes: A61C17